高Crフェライト系ステンレス鋼を含む各種ステンレス鋼の長期暴露試験による耐候性

摘要

ステンレス鋼は優れた耐候性を活かし，屋根材や外装rn材などの建材用途に用いられている。近年のウオーターrnフロント開発等に伴い，海岸近くの建築物の屋板材や外rn装材にステンレス鋼が適用されるケースが増加していrnる。建材用途には，汎用耐食鋼であるSUS304やSUS316rnが使用される場合が多い。このような汎用耐食鋼は，海rn塩粒子が飛来する海岸環境において孔食を生じるが，腐rn食の進行は横やかであり，機能性の面では問題ないものrnと考えられている1～3）。%The atmospheric corrosion resistance of several stainless steels including high Cr ferritic stainless steels was evaluated from appearance (rating number) and pitting depth. The results obtained are summarized as follows.rn(1) Common austenitic stainless steels SUS304 and SUS316 were wholly covered with light rust in Okinawa (coast area). Such rust was less found in NSS445M2 (22Cr-lMo), NSS447M1 (30Cr-2Mo), NSSURC (25Cr-25Ni-5Mo-0.13N) and NSS329M2 (25Cr-6.5Ni-3Mo-0.14N).rn(2) The atmospheric corrosion resistance was improved with pitting index (Cr+3.3Mo+16N) increasing. Stainless steel which pitting index is over 26 like NSS445M2 shows good corrosion resistance in Okinawa.rn(3) The appearance of NSS445M2 with 2D, 2B, 2DR and HL finishing keep fine after 15 years in several environment, Niigata (urban area), Kiryu (inland area), Amagasaki (industrial area) and Okinawa.rn(4) Pitting depth of NSS445M2 was less than 0.1mm after 10 years in Okinawa, and will not grow afterwards.rn(5) Therefore, NSS445M2 is suitable material for marine environmental architectural structures.